Written by Chris Thom
Spoon Feed
Diaphragm ultrasound accurately predicted which COPD patients undergoing non-invasive ventilation would require intubation.
The diaphragm deserves your POCUS attention
This single-center prospective study recruited 111 patients with acute COPD exacerbation who required non-invasive ventilation (NIV). Emergency physicians with specific diaphragm ultrasound training assessed diaphragmatic function on ultrasound via two metrics. Diaphragmatic excursion (DE) was measured prior to initiation of NIV and diaphragmatic thickening fraction (DTF) was measured at the 2-hour mark following NIV initiation.
22.5% of patients required intubation. Using a cutoff of 1.2 cm, DE had a sensitivity of 88% and specificity of 84.9% for predicting NIV failure. Employing a threshold of 20%, DTF had a sensitivity of 92% and specificity of 93%. In multivariable logistic regression analysis, DTF was found to be an independent factor associated with NIV failure.
How will this change my practice?
We use multiple clinical and diagnostic tools to determine who is at risk for decompensation. There is mounting evidence that diaphragm ultrasound can be a useful adjunct in our toolbox for several respiratory disorders. I’ll be adding this information into my assessment of whether a patient is likely to progress to intubation. Perhaps it may someday even help resolve disagreements about whether the patient belongs in the MICU or on the Medicine floor.
POCUS Pro-Tips:
While both DTF and DE are easy to pick up, DE is a bit friendlier to the novice user. DE is obtained with the probe between the midclavicular and anterior axillary lines, with the ultrasound “flattened” against the abdominal wall and the ultrasound beam angled into the thorax. You’ll then apply M-mode to quantify the DE during inspiration / expiration. DTF is a percentage metric, similar to the IVC collapsibility index. Here you need the probe on the right side between the mid and anterior axillary line in the 8th to 11th rib spaces. The diaphragm will be a three-layered structure between the pleural and peritoneal membranes. M-mode is also used here to measure the diaphragm thickness in inspiration and expiration. This video is particularly helpful in how to perform these measurements.
Source
Diaphragmatic ultrasonographic evaluation as an assessment guide for predicting noninvasive ventilation failure in acute exacerbation of chronic obstructive pulmonary disease. Am J Emerg Med. 2025 Jul;93:13-20. doi: 10.1016/j.ajem.2025.03.025. Epub 2025 Mar 17. PMID: 40120416.
